A grinder according to the known prior art usually comprises:                a grinding arrangement, which is used to grind coffee beans and comprises for this purpose a first grinding element and a second grinding element, wherein the first grinding element can be rotated around a rotational axis relative to the second grinding element in such a way that coffee beans are brought between the two grinding elements and ground into a coffee powder;        a rotatably mounted entrainer wheel which is mounted rotatably beneath the grinding arrangement and is used for the onward transport of the coffee powder ground by the grinding arrangement;        an exit channel, via which the ground coffee powder can leave the grinder, wherein the powder is conveyed to the exit channel by means of the entrainer wheel.        
There are various types of grinding arrangements which differ in respect of the shape and arrangement of the grinding elements, e.g. conical grinders, disc grinders, etc.
Various forms of entrainer wheels are known. An entrainer wheel can comprise, on the upper side, a region extending around the rotational axis of the entrainer wheel (hereinafter “transport region”), onto which the coffee powder ground by the grinding arrangement can fall. In order that the coffee powder ground by the grinding arrangement can fall onto the transport region of the entrainer wheel, the entrainer wheel has to be suitably disposed relative to the grinding arrangement.
For example, grinders with an entrainer wheel are known, which are constituted conically (see EP-A-1964498, FIG. 1). In DE-A-4418139, an entrainer wheel (also referred to as a “delivery plate”) is shown, which is provided at its outer edge with so-called upwardly directed air vanes (see FIGS. 3 and 4). The transport region of this entrainer wheel is constituted very slightly conical, i.e. flat falling away radially outwards in a linear manner. Through rotation of the entrainer wheel, coffee powder located on the transport region is on the one hand carried along around the rotational axis of the entrainer wheel and on the other hand moves radially outwards due to a centrifugal force. Since the transport region falls away slightly in a linear manner, the movement directed radially outwards is additionally assisted.
Known entrainer wheels can comprise a plurality of entrainer vanes, which are disposed on the upper side of the entrainer wheel in the transport region and extend radially with respect to the rotational axis. When the entrainer wheel is rotated, these entrainer vanes carry ground coffee powder ahead of them in the rotational direction, i.e. along a path around the rotational axis.
There are known from DE-A-441813 entrainer vanes (“entrainer vanes 21” according to FIG. 3), which are disposed at the outer edge of the entrainer wheel (9) and extend over a relatively short distance (compared to the width of the transport region) of the entrainer wheel. A drawback is that the coffee powder is not conveyed very efficiently around the rotational axis by means of these entrainer vanes, but rather swirls up. Powder falling on the entrainer wheel remains in the transport region during a number of revolutions of the entrainer wheel before it reaches the exit channel, so that a small delivery capacity results.
In EP-A-1964498, the entrainer vanes (“ribs 261” according to FIG. 1 and section [0013]) extend radially with respect to the rotational axis of the entrainer wheel and their height diminishes to zero in the direction of the rotational axis. The drawback thus arises that the ground powder can slide onto the upper side of the entrainer vane, which leads to clogging-up, so that a rotation of the entrainer wheel is impeded or the entrainer wheel becomes blocked. Stale coffee powder can accumulate on the entrainer vanes and mix with freshly ground powder, which adversely affects the taste of the brewed coffee.